Steel balls used in ball bearings, etc., are first made from wire materials into roughly spherical blanks having flashes. Then, they are subjected to flashing process to remove such flashes, heat treatment to impart the required strength and durability to the balls, grinding process thereafter, and lapping process to finish the balls with high accuracy after the grinding process.
FIG. 7 illustrates a steel ball machining apparatus 70 of prior art used in the above-mentioned flashing, grinding, and lapping processes. The apparatus 70 comprises a machining mechanism 76 having a rotary plate 72 and a stationary plate 74, and a conveyor 80 having a vessel 82 for supplying steel balls 78 between the rotary plate 72 and the stationary plate 74 and receiving steel balls 78 therefrom. The conveyor may be either a rotor conveyor type, a water propeller type or a bucket elevator type. In the flashing process, the rotary plate 72 and the stationary plate 74 have the respective ball grooves (not shown); and are axially pressed together with the balls held therebetween. In the grinding and lapping processes, balls are fed between the rotary plate 72 and the stationary plate 74 with a grinding fluid, the surface plate 74 having V- or R-shaped grooves and the rotary plate 72 having ball grooves with a predetermined depth.
The steel balls 78 supplied by the conveyor 80 are held between the rotary plate 72 and the stationary plate 74 and processed while rolling along the grooves. After making almost a round held between the rotary plate 72 and the stationary plate 74, the balls 78 are discharged to the conveyor 80. The balls 78 circulate through the machining mechanism 76 and the conveyor 80 until the predetermined dimensional accuracy is attained.
The flashing process is mainly to remove flashes. Most of the flashes will fall from the space between the rotary plate 72 and the stationary plate 74 along with the grinding fluid. However, some of them in fact are returned to the conveyor 80 and are fed into the machining mechanism 76. Consequently, it is possible that the flashes will damage the ball grooves of the rotary plate 72 and the stationary plate 74. In addition, it is also possible that wire materials which failed proper machining during the initial forming process are mixed with the balls and fed to the machining mechanism 76 damaging the grooves of the rotary plate 72 and the stationary plate 74.
In the grinding and lapping processes, a grinding wheel is utilized as the rotary plate 72. When steel balls 78 are fed to the machining mechanism 76, the grinding wheel oftentimes breaks off. Such chips of a grinding wheel will also fall from the space between the rotary plate 72 and the stationary plate 74 along with the grinding fluid. But, some of them are accidentally fed by the conveyor 80 to the machining mechanism 76 damaging the ball grooves of the rotary plate 72 and the stationary plate 74. Furthermore, in case balls having flaws or cracks are fed into the machining mechanism 76, they will also give rise to the possibility of a similar damage.
Thus, the object of the present invention is in the first place to provide a steel ball machining apparatus which is capable of removing foreign matter which are apt to accidentally mix with the processed steel balls.
Secondly, the object of the present invention is to provide a steel ball machining apparatus which is capable of protecting the ball grooves in the rotary plate and the stationary plate by eliminating foreign matter.
A further object of the present invention is to provide a steel ball machining apparatus which is capable of guaranteeing a predetermined level of quality of the finished steel balls by protecting the ball grooves of the machining plates as mentioned above.